1. Field of the Invention
The present invention relates to a numerical controller capable of shortening the cycle time in a turning based on a composite fixed cycle.
2. Description of the Related Art
A numerical controller reads out a processing program stored in a memory, and controls a machine tool by driving a servo motor and a spindle motor in accordance with this processing program.
A complex fixed cycle command in a numerical controller programs a workpiece machining pattern and performs a turning in accordance with this workpiece processing program. As shown in FIG. 9, in a cycle operation, the following actions are carried out: (1) positioning at start point (A) of turning; (2) cutting by tool t; (3) withdrawal operation from workpiece; and (4) positioning of workpiece W again at start point; and the actions (1) to (4) are repeated until machining of the workpiece W is completed.
As an example of prior art relating to cycle machining of this kind, Japanese Patent Application Laid-Open No. 2015-011669 discloses a numerical controller having a start point path shortening function for a complex fixed cycle, wherein processing is carried out to set a linear path from a cutting end position of the cycle to a cutting start position of a next cycle, in a complex fixed cycle, thereby shortening the cycle time of the complex fixed cycle.
Furthermore, Japanese Patent Application Laid-Open No. 2014-195856 discloses machining of a shaft-like member, wherein a first tool and a second tool are held on a common tool holder so as to have a positional relationship in which the respective tip sections thereof are displaced by 180°, and the tip sections of the first tool and the second tool are then arranged in a groove formed in the shaft-like member, and while the shaft-like member is rotated about the central axis thereof, the tip sections of the first tool and the second tool are moved in the direction of the central axis from inside the groove, and the outer circumferential surface of the shaft-like member is cut (turned) by the first tool and the second tool.
However, in the operation of the turning shown in FIG. 9, the direction of the turning is unidirectional, and therefore when the turning of one cycle has been completed, it is necessary to return the tool to the start point of the turning in order to carry out the turning of the next cycle. Time unrelated to the turning is necessary for the operation of returning to the start point, and hence there is a problem in that the cycle time becomes correspondingly longer.
In practice, the technology disclosed in Japanese Patent Application Laid-Open No. 2015-011669 described above contributes to a certain extent to improving the cycle time, but the direction of the turning direction remains unidirectional and furthermore, when making a cutting insertion, since the next turning is carried out after returning through the distance that has been cut, then there remains a problem in that time is always required to return to position.
Moreover, in the technology disclosed in Japanese Patent Application Laid-Open No. 2014-195856 described above, since the two tools move and perform turning in the same direction, then the turning direction is still unidirectional, and furthermore, when making a cutting insert, since the next turning is carried out after returning through the distance that has been cut, then there is a problem in that time is always required to return to position.